What did I forget to order?

The small boards to repair the treadmill are finally here. I have only had all the parts here and the layout for the board done for the past several months. I think this board should be beefy enough to truly fix the problem.

The history on the treadmill is a long one. We ended up with a treadmill with a faulty display that my wife gave me permission to hack on to try to fix it, after all I'm a EE right? I should be able to fix everything, even if I don't have a schematic or nice set of test equipment at home. Luckily the fault here was just the contrast on the display going out and the negative voltage generator circuit was easily accessible.

So I pulled up the datasheets on the IC's and capacitors they were using which of course turned out to be the cheapest bare minimum parts they thought they could get away with. So I bought and replaced the caps and voltage inverters with better versions of the same parts and put it all back together. It worked!! For about a month. Measuring all the voltages in the circuit showed that once again, even with the better parts, the voltage inverters were failing. At that point I gave up trying to improve the original voltage inverter circuit and just design my own and drop it in.

In the end I decided it would be a lot less hassle and much more robust if I simply took a known good design and dropped that in. So I've got a board put together that includes a nice TI based inverter that is probably way overkill for this but should be able to take the abuse that kept frying the original inverter circuit.

The whole thing is basically the TI PTN04050 with the necessary support components. I also have a different configuration set up to be able to use the part as a variable negative voltage generator instead of the fixed configuration shown above. I'll post another update once I get it installed and working.

The treadmill fix ended up being a pretty small board so I added the embedded data recorder to use up the rest of the real estate on the cheap PCBExpress boards.

I also received the MSP430 dev kit I ordered in the previous post at a great price and verified it does indeed have the complete USB programmer which is listed by itself as $25 more than the dev kit. I also received my box full of parts which I checked against my BOM. And of course something got left out and I remembered something else I had planned for but forgotten because it wasn't on the BOM.

Fortunately the item left of the BOM was the transformer that you have to direct order from coilcraft and that's ok because I'm not sure what ratio I want yet. Placing the thermoelectric cooler against the cold window here in Seattle had it generating 200mV initially so I need to look at the energy harvesting circuit and the long term equilibrium voltage generated to determine which transformer to use.

I also need to go back to DigiKey and get a couple of the FTDI uart to USB cables that run straight from a 3.3V uart. Got spoiled to those at work and need some for the home projects as well.

Once I get the treadmill up and running (hopefully for longer than a month this time), I will start putting together the embedded data recorder and get started on both the embedded code and trying to get something together on the PC side to do something useful with the data.

Embedded Data Recorder

So I have finished the schematic and layout of the data recorder board I've been planning on putting together. Schematic and layout information can be found here. I've ordered the boards from PCBExpress. They should be here in a few days along with most of the parts which I'm getting from Digi-Key.

Also starting to play more with the MSP430 boards that I've been gathering. If you're looking for a cheap way to get into microcontrollers I'm not sure there's a cheaper way than the Texas Instruments Launchpad.

For $4.30 you get a socketed MCU with a built in JTAG interface a USB interface and headers for external connections. I couldn't see not getting a couple of them.

Then there's the EZ430 USB stick I picked up last year. Also low price and you can detach the small MCU boards once programmed and have them run in your own system.

Very reasonably priced and I also bought several daughter boards so I can use them in a variety of projects. Again they provide connections to all the pins and should prove handy for small projects.

I also ran across an interesting bit of pricing on Digi-Key where you can actually buy a small dev kit with the USB Flash Emulation Tool (FET) programmer for less than the programmer alone. This tool will allow you to program any MSP430 through the standard JTAG interface. Digi-Key currently has them listed at $76 for the kit and $99 for the programmer. Mine should arrive in the next couple days so I can verify Edit: It is verified that you do get the full FET pod. I have no idea how long that pricing will last.

Oh yeah, I almost forgot this was here

Well it's been months since I started tinkering and not really a lot has moved although I have been busy working.

I've come into some free time so I'm moving ahead with a couple of projects I've been trying to get going for a looong time.

First is the MSP430 board I've been thinking about for a long time. I'm currently finishing up the schematic and layout (PCBExpress) so that I have a baseline setup to work from. I've put on a 2MB serial flash, accelerometer, gyro, current sense, switches, LEDs, and an energy harvesting circuit based on Linear Technologies LTC3108. I'm designing it to fit into a small project box I'm scavenging from audio crossovers I bought from The Electronic Goldmine. Ideally this will be able to run forever with the energy harvesting and serve as a long term data logger.

Second is the negative voltage generator circuit to fix the defunct display on our NordicTrack treadmill.

Other things I'm currently thinking about and trying to work in to the schedule include FPGA based test equipment, wireless for the data loggers (I'm leaning towards the ANT bluetooth protocol currently), getting some imaging stuff going, tinkering with the android SDK, learning Python for the PC interface for a lot of these things, and playing with the MSP430 Value line kits $4.30 a piece!!!! and the 2013 parts I got a year or so ago.

I'll see if I can't be a little more consistent with posting updates from here on out :)